A Function for Phosphoinositide 3-Kinase β Lipid Products in Coupling βγ to Ras Activation in Response to Lysophosphatidic Acid

作者：Armelle Yart, Serge Roche, Reinhard Wetzker, Muriel Laffargue, Nicholas K. Tonks, Patrick Mayeux, Hugues Chap, Patrick Raynal · 发表于：Journal of Biological Chemistry · 年份：2002 · DOI：10.1074/jbc.m110411200 · 被引用次数：77 · 研究领域：Protein Kinase Regulation and GTPase Signaling、PI3K/AKT/mTOR signaling in cancer、Receptor Mechanisms and Signaling

Although Gbetagamma is thought to mediate mitogen-activated protein kinase (MAPK) activation in response to G protein-coupled receptor stimulation, the mechanisms involved in this pathway have not been clearly defined. Phosphoinositide 3-kinase (PI3K) has been proposed as an early intermediate in this process, but its role has remained elusive. We have observed that dominant negative mutants of p110beta, but not of p110gamma, inhibited MAPK stimulation in response to lysophosphatidic acid (LPA). The role of p110beta was located upstream from Ras. To determine which of the lipid or protein kinase activities of p110beta were important for Ras activation, we produced a mutant p110beta lacking the lipid but not the protein kinase activity. This protein displayed a dominant negative activity similar to a kinase-dead mutant, indicating that p110beta lipid kinase activity was essentially involved in Ras activation. In agreement, overexpression of the lipid phosphatase PTEN was found to specifically inhibit Ras stimulation induced by LPA. In addition, we have observed that the PH domain-containing adapter protein Gab1, which is involved in p110beta activation during LPA stimulation, is also implicated in this pathway downstream of p110beta. Indeed, both membrane redistribution and phosphorylation of Gab1 were reduced in the presence of PI3K inhibitors or dominant negative p110beta. Downstream of Gab1, the tyrosine phosphatase SHP2 was found to mediate Ras activation in response to LP...